RFC0077

Network Working Group J. Postel
Request for Comments: 77 UCLA
NIC 5604 20 November 1970
Network Meeting Report
This is a report on a series of three Network Working Group meetings at
the Fall Joint Computer Conference, November 16, 17 and 18 in Houston,
Texas. The meeting will be lumped together and ideas may or may not be
identified as to their originator. The meetings were chaired by Steve
Crocker.
The meetings began with a listing of topics of concern.
1) A site or group should be designated as protocol testers. As NCP's
are implemented they should be subjected to comprehensive testing by
an independent group.
2) The Host-Host protocol needs reworking in several areas: error
control, overload conditions, allocation of resources, status
information, and system crash problems.
3) The immediate need for specification of TELNET, the third level
program which allows people to pass through their local hosts and use
remote hosts. TELNET must provide facilities to log in at a distant
site, run programs, transmit files, and call for help. This call for
help is likely to mean getting a systems programmer at the remote
site "taking control" of the user console.
4) The documentation of systems on the network must become available to
all sites. This is to be done by the NIC with the cooperation of the
other sites. Particularly useful will be on-line documentation. It
is suggested that each site have an identical hard copy device (e.g.
a line printer) suitable for reproducing documents.
5) The use of graphics consoles on the network will require a graphics
protocol. People interested in this problem should write position
papers on such a protocol. A meeting may be held between the authors
of such papers if sufficient interest develops. The papers should be
distributed as NWG/RFC's before 1 January 71.
6) Some sites must account for use of their computer resources, thus
there must be some network accounting scheme. Sites can be
categorized as Research Centers vs. Service Centers. The Service
centers tend to have big machines, lots of users, and accounting
problems; while the Research Centers tend to have specialized
hardware, a small number of users, and no accounting at all.
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RFC 77 Network Meeting Report 20 November 1970
7) Some people are interested in the network as an object of study. In
particular UCLA-Computer Science, and BBN wish to perform
measurements on the network. Is it appropriate to ask the NCP to
keep statistics?
After this opening some discussion followed.
It was generally felt that changes to the protocol should be made in
bunches and at about six-month intervals rather than a continuous stream
of small changes. Also that a lead time of three months was not over
optimistic. The proposed change to the IMP-Host protocol to get rid of
marking was generally approved but it will not be implemented for some
time since casual changes to the protocol are undesirable. Tom
O'Sullivan suggested that perhaps new and old protocols could work
together, that is the new protocol would support the old one as well as
provide better mechanisms where possible. Steve Crocker suggested that
a new protocol might be developed as a private experimental protocol
between two or three sites.
It was stressed that it is necessary that the network be used to gain
experience, and that we should get teletype-like console use of remote
systems going before we get too involved in graphics. Perhaps the
graphics protocol should be developed by a different set of people. The
scheduling of a graphics protocol meeting was thus discouraged, but
papers should still be written. Strong feelings were expressed in
favour of first developing use of remote subsystems and file
transmission instead of worrying about graphics at this stage. It was
suggested that development of protocols at the higher levels be driven
by applications.
Documentation will be a major concern for network users. Several people
mentioned that users at their sites have already begun to inquire about
the network. As Eric Harslem put it "What does the ARPA Network have to
offer?" Some sites (Multics, SRI) keep system documentation on-line.
It was suggested that the trillion bit store be used to keep on-line
documentation of all systems.
At this point Doug Engelbart gave a presentation on the Network
Information Center (NIC). The goals or services of NIC have not been
well defined by anyone and have been left up to NIC to define. NIC has
decided that one urgent task is to make information about the network
and the host systems on the network available to users of the network.
Doug has found that some people feel threatened by the revelation of
their documentation inadequacy. Doug's project at SRI has built up a
system that allows the user to create catalogs and indices into a
collection of information. The system has a master catalog of all
information files. Each user may have a number of private (or shared)
catalogs. The system provides a means of examining on-line the catalogs
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RFC 77 Network Meeting Report 20 November 1970
and amending them. The system also provides a means to examine any
information file which happens to be on-line and for creating new
information files on-line.
Several problems will delay the NIC from coming on the network. One of
these is the switch from the XDS-940 to the PDP-10 (TENEX). The switch
is being made because the 940 system is inadequate to handle the
anticipated load. At first it was planned to offer service on the 940
and switch to the 10 when it came up, but too much effort would be
required for a very small payoff.
Doug explained the working of the Network Dialoge System. At each site
there is a communication agent and a technical liaison officer. The
agents will be trained by NIC to use the facilities of NIC to get
information about the Network and other sites. The agents will acquire
from NIC documents of interest to users at the local site, be able to
contact NIC at a toll free number, and should have an on-line console
into the network (and therefore NIC). Thus the Network Dialoge System
is a network of people (the agents).
Steve Crocker then brought us up to date on the status of the network.
He drew a picture of what is connected and what is proposed. He
discussed the level of implementation at various sites. Eric Harslem
mentioned that RAND and UCSB had conducted tests of their NCP
implementations last week (10 Nov 70) and that things worked well.
Frank Heart announced that BBN was planning the development of a
"Terminal" IMP. The Terminal IMP would support some large number of a
wide range of consoles as well as provide the normal IMP functions.
At this point we broke and scheduled to reconvene Tuesday morning.
The Tuesday meeting started with Doug giving another pass at explaining
the SRI system at a more detailed level. The basic thing to deal with
is the collection. The user can query over the collection or over sub
collections. The user can obtain bibliographic references of three
kinds: a) full references, b) first line, c) author indexed.
Information files of the collection may be on-line, in tape libraries,
or only in hard copy. It is suggested that much data could be kept at
other network sites, for example the trillion bit store and before that
perhaps on disk at UCSB. If files are kept at other sites then the
system must be able to retrieve them automatically when they are
requested. The subsystem to be used is called TODAS. TODAS is an
evolving program and the documentation of TODAS is inadequate. In
TODAS, file are organized hierarchically, each paragraph is numbered,
and it is possible to do context analysis on the text.
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RFC 77 Network Meeting Report 20 November 1970
Doug then mentioned some things about the console interaction. This
raised a question about half vs. full duplex and line oriented vs.
character oriented systems. The remainder of the meeting revolved
around this issue.
I shall try to define the terms as I understand them for purpose of
clarity in the following. Half duplex is the situation where the
console, a peripheral processor or some very low level software, echos
the character entered. The console can not be used to input data while
output is in progress. Full duplex is the situation where the character
typed is echoed by software, and input can be done at the same time as
output. In line oriented systems the user enters a complete line
terminated by an extra sensitive and of line character (e.g. carriage
return). Often the keyboard is then locked until after the next output.
In character oriented systems each character the user enters is
interpreted by software before it is echoed and the echo may be
different from the character entered. In particular after a few
character the software may guess what the user wants and complete the
line for him. The following chart will be used for clarity.
| Half Duplex | Full Duplex
______________|_____________|_____________
| |
Character | |
Oriented | type1 | type2
| |
______________|_____________|_____________
| |
Line | |
Oriented | type3 | type4
| |
______________|_____________|_____________
It was discovered that many people don't really know where their own
systems fit in this chart and are very vague about what it means to
interact with a system in a different than their own. Doug stated that
NIC has a system of type 2 but would try to provide service to all types
of systems. The following table shows systems with their interaction
type and categorization as to Research vs. Service Center.
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RFC 77 Network Meeting Report 20 November 1970
System Interaction Type Categorization
UCLA - Sigma-7 2 - char, full Research
UCLA - 360/91 3 - line, half Service
MIT - Multics 3 - line, half Service
SDC 3 - line, half ?
RAND 3 or 4 - line, ? ?
SRI 2 - char, full ?
Al Vezza promised to study this problem and to circulate his results as
an NWG/RFC. It was pointed out that line oriented systems usually allow
line editing of the form "delete last character" (back space) and
"delete line", however this feature does not alter their classification
as to interaction type. Concern arose over what do line oriented
systems expect to receive from the network for a connection acting as
console input to a subsystem. Steve Crocker made the suggestion that
when using a line oriented system transmission be in lines. More
precisely that transmission be in strings of the following form.
n c1 c2 ...cn
where 1 <= n <= 120 (n is eight bits)
and if ci is an "end of line" character then i = n
This suggestion was not immediately accepted and some discussion took
place regarding the significance of Host-Imp-Host message boundaries.
Doug brought up file transmission and the problem of finding the end of
the file, which provoked more discussion. At this point the meeting
broke up with a third session scheduled for 8:00 p.m. Wednesday evening.
The Wednesday meeting began with the suggestion that at future xJCC's
there be an official ARPA Network hotel with a block of rooms on one
floor and a nearby meeting room for networkers. This suggestion was
favored by all.
Steve Crocker asked how people felt about these meetings. The general
feeling was that the meetings were very useful and should occur about 3
months apart. Al Vezza pointed out that meetings this size (15 - 30
people) are good for bringing up problems but not for putting them down.
Steve proposed that 3 or 4 people be designated to solve particular
problems. Al responded that 3 people can't legislate. That any such
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RFC 77 Network Meeting Report 20 November 1970
solution must be considered in the same way as a proposal by an
individual.
Steve persuaded Peggy Karp to act as NWG/RFC editor. This is a job
independent of cataloging RFC's or assigning numbers (functions now
performed by NIC). The RFC editor will only categorize RFC as "hot
issues", current, out of date, or superseded.
The subject of Logger protocol -- that is, how to get the first
connection -- needs to be officially defined. NWG/RFC #66 suggests one
way. Eric Harslem will revise this and send it out as proposed official
protocol. Ed Myer will also send out a proposal.
Steve then opened up discussion of the topics of the previous meeting by
suggesting we talk about the following: Message boundaries, half duplex
vs. ull duplex, line oriented vs. character oriented, file
transmission, byte counts in messages, byte sizes and transactional
units. It was proposed that transactions on the command link (i.e.
between NCP's) be always in multiples of eight bits. This mean that the
length field in the ECO, ERP, and ERR commands will always have three
low order zeroes. This was approved. Steve then proposed that
connections could be established with a declared byte size and a maximum
record length in bytes. Transactional units on this type of connection
would be of the form
n c1 c2 c3 ... cn
where 0 <= n <= max record length
if n = 0 then the transactional unit acts like a semaphore. Steve
suggested that we should look into the theory of information exchange,
particularly along the lines of Richard Kaline (NWG/RFC #60). Perhaps
for each information unit sent there should be some status response.
The next question was on file transmission. In particular, how do you
find the end? Frank Heart suggested that with each portion there be a
flag indicating "this is not the end" until in the last portion the flag
is switched to indicate "this is the end". Eric Harslem suggested that
each portion should have an "opcode" field, a length field, and the text
which is length bits (bytes?) long. This appears to be like the data
types proposed at the Lincoln Lab meeting last spring. Ed Myer proposed
that two connections be used, one for the file transmission and the
other to control it. The file control connection would specify the data
connection and indicate that transmission as about to start. After the
sender had completed the file transmission he would send on the file
control link the total number of bits sent. The receiver would then
know how many bits to receive and exactly where the end of the file
should be. Bob Metcalfe was concerned that some of the proposals mixed
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RFC 77 Network Meeting Report 20 November 1970
control information with data and felt that perhaps this mixing should
be avoided.
Steve asked if anybody could suggest an advisor we might talk about
these problems. Bob Metcalfe suggested Anatol Holt. Bob Sundberg
suggested George Mealy. Eric Harslem and Peggy Karp suggested that
people who worked on the COIN System might be helpful. Frank Heart
suggested that no one has solved these problems.
Steve proposed that Service Centers offer line oriented interaction with
no echoing of the input. Any simple editing (e.g. back space) would be
done at the using site. Ed Meyer suggested that there be official
protocols for both line oriented and character oriented interaction.
Steve promised to write a NWG/RFC clarifying the issues and laying out
the arguments on full transactions, byte counts, and accumulating data
on the receive side.
It was felt that these were hard problems that needed more thought.
Thus the meeting was adjourned with the request that people circulate
any ideas or proposals as NWG/RFC's. Ed Myer took notes and agreed to
also prepare a NWG/RFC summarizing these meetings.
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